1. Field of the Invention
The invention is generally related to the use of a remotely operated vehicle (ROV) from a drone vessel for underwater work and more particularly to means used to restrain the umbilical line between the drone vessel and ROV.
2. General Background
Many underwater operations, such as drilling for and production of oil and gas, installation and maintenance of offshore structures, or laying and maintaining underwater pipelines require the use of a remotely operated vehicle (ROV) or robotic tooling.
The deployment of an ROV is typically achieved by launching the unit from either a bottom founded or floating host platform, a dynamically positioned marine vessel dedicated specifically for the purpose of supporting an ROV, e.g. an ROV support vessel (RSV), or any such surface vessel with sufficient size and characteristics that provide a suitably stable platform for the launching and recovery of an ROV.
Both bottom founded and floating host platforms are fixed in position at the site and are normally engaged in collateral activities such as drilling and offshore production or construction. Thus, the operations of the ROV are limited according to the distance that the ROV can travel from the host platform as well as by restrictions in operating periods due to the collateral activities of the host platform.
In the case of dedicated vessel deployment such as an RSV, significant costs are associated with operation of a fully founded marine vessel and its mobilization to and from the ROV work site. Typically, a dedicated RSV may have a crew of twenty and a considerable cost not directly related to the operation of the ROV.
ROV operation and monitoring is controlled from the host platform or RSV by means of an umbilical line between the host platform or RSV and the ROV. It can be seen from this that the operational distance of the ROV is directly related to the length of the umbilical line.
A remotely operated near surface drone vessel with adequate stability that is capable of launching, controlling, and recovering an ROV eliminates the limitations associated with operation from a fixed host platform and reduces the expense associated with a manned, dedicated RSV.
The remotely operated drone vessel requires an umbilical line, storage drum and winch to launch, control, and recover the ROV. The stability of the drone vessel can be adversely affected by deployment of the ROV. This can occur from lateral loads imposed on the drone vessel from the umbilical line and ROV that effectively decreases the stability of the drone vessel. This leaves a need for a means of reducing the effects of lateral loads applied by the umbilical line and increasing the stability of the drone vessel.